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1
Content available Diagnosis of multiple faults of an induction motor based on Hilbert envelope analysis
Kabul Ahmet, Ünsal Abdurrahman
Metrology and Measurement Systems
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2022
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Vol. 29, nr 1
191--205
EN
Three phase induction motors are widely used in industrial processes and condition monitoring of these motors is especially important. Broken rotor bars, eccentricity and bearing faults are the most common types of faults of induction motors. Stator current and/or vibration signals are mostly preferred for the monitoring and detection of these faults. Fourier Transform (FT) based detection methods analyse the characteristic harmonic components of stator current and vibration signals for feature extraction. Several types of simultaneous faults of induction motors may produce characteristic harmonic components at the same frequency (with varying amplitudes). Therefore, detection of multiple faults is more difficult than detection of a single fault with FT based diagnosis methods. This paper proposes an alternative approach to detect simultaneous multiple faults including broken rotor bars, static eccentricity and outer/inner-race bearing faults by analysing stator current and vibration signals. The proposed method uses Hilbert envelope analysis with a Normalized Least Mean Square (NLSM) adaptive filter. The results are experimentally verified under 25%, 50%, 75%, 100% load conditions.
2
Content available Multiple fault parameter estimation of a fully assembled turbogenerator system
Lal M.
Archive of Mechanical Engineering
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2018
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Vol. LXV, nr 2
233--252
EN
The present article investigates the dynamic behavior of a fully assembled turbogenerator system influenced by misalignment. In the past, most of the researchers have neglected the foundation flexibility in the turbogenerator systems in their study, to overcome this modelling error a more realistic model of a turbogenerator system has been attempted by considering flexible shafts, flexiblecoupling, flexible bearings and flexible foundation. Equations of motion for fully assembled turbogenerator system including flexible foundations have been derived by using finite element method. The methodology developed based on least squares technique requires forced response information to quantify the bearing–coupling–foundation dynamic parameters of the system associated with different faults along with residual unbalances.The proposed methodology is tested for the various level of measurement noise and modelling error in the system parameters, i.e., 5% deviation in E (modulus of elasticity) and ρ (density), respectively, for robustness of the algorithm. In a practical sense, the condition analyzed in the present article relates to the identification of misalignment and other dynamic parameters viz. bearing and residual unbalance in a rotor integrated with flexible foundation.
3
Content available Estimation of speed dependent fault parameters in a coupled rotor-bearing system
Lal M., Satapathy M.
Archive of Mechanical Engineering
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2018
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Vol. LXV, nr 3
327--347
EN
In rotating machineries, misalignment is considered as the second most major cause of failure after unbalance. In this article, model-based multiple fault identification technique is presented to estimate speed-dependent coupling misalignment and bearing dynamic parameters in addition with speed independent residual unbalances. For brevity in analysis, a simple coupled rotor bearing system is considered and analytical approach is used to develop the identification algorithm. Equations of motion ingeneralized co-ordinates are derived with the help of Lagrange’s equation and least squares fitting approach is used to estimate the speed-dependent fault parameters. Present identification algorithm requires independent sets of forced response data which are generated with the help of different sets of trial unbalances. To avoid/suppress the ill-conditioning of regression equation, independent sets of forced response data are obtained by rotating the rotor in clock-wise and counter clock-wise directions, alternatively. Robustness of algorithm is checked for different levels of measurement noise.
4
Content available The On-line Evolutionary Method for Soft Fault Diagnosis in Diode-transistor Circuits
Korzybski M., Ossowski M.
International Journal of Electronics and Telecommunications
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2015
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Vol. 61, No. 1
109-115
EN
The paper is devoted to diagnostic method enabling us to perform all the three levels of fault investigations - detection, localization and identification. It is designed for analog diode-transistor circuits, in which the circuit’s state is defined by the DC sources’ values causing elements operating points and the harmonic components with small amplitudes being calculated in accordance with small-signal circuit analysis rules. Geneexpression programming (GEP), differential evolution (DE) and genetic algorithms (GA) are a mathematical background of the proposed algorithms. Time consumed by diagnostic process rises rapidly with the increasing number of possible faulty circuit elements in case of using any of mentioned algorithms. The conncept of using two different circuit models with partly different elements allows us to decrease a number of possibly faulty elements in each circuit because some of possibly faulty elements are absent in one of two investigated circuits.
5
Content available Multiple soft fault diagnosis of BJT circuits
Tadeusiewicz M., Hałgas S.
Metrology and Measurement Systems
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2014
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Vol. 21, nr 4
663--674
EN
This paper deals with multiple soft fault diagnosis of nonlinear analog circuits comprising bipolar transistors characterized by the Ebers-Moll model. Resistances of the circuit and beta forward factor of a transistor are considered as potentially faulty parameters. The proposed diagnostic method exploits a strongly nonlinear set of algebraic type equations, which may possess multiple solutions, and is capable of finding different sets of the parameters values which meet the diagnostic test. The equations are written on the basis of node analysis and include DC voltages measured at accessible nodes, as well as some measured currents. The unknown variables are node voltages and the parameters which are considered as potentially faulty. The number of these parameters is larger than the number of the accessible nodes. To solve the set of equations the block relaxation method is used with different assignments of the variables to the blocks. Next, the solutions are corrected using the Newton-Raphson algorithm. As a result, one or more sets of the parameters values which satisfy the diagnostic test are obtained. The proposed approach is illustrated with a numerical example.
6
Content available Diagnostyka złożonych procesów przemysłowych - ograniczenia, wymagania, problemy
Kościelny J. M., Syfert M., Bartyś M.
Pomiary Automatyka Kontrola
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2011
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R. 57, nr 7
801-805
PL
W artykule omówiono uwarunkowania i ograniczenia występujące w diagnostyce złożonych instalacji w przemyśle chemicznym, petrochemicznym, energetycznym itp. Określono wymagania stawiane systemom diagnostycznym dla takich instalacji oraz scharakteryzowano problemy istotne w procesie projektowania systemów diagnostycznych. Do problemów tych zaliczyć należy: zmienność struktury obiektu w trakcie eksploatacji, opóźnienia powstawania symptomów prowadzące do fałszywych diagnoz oraz występowanie uszkodzeń wielokrotnych. Podano sposoby rozwiązania tych problemów. Zostały one zastosowane przy realizacji systemów modelowania, diagnostyki i nadrzędnego sterowania procesów AMandD oraz DiaSter.
EN
Limitations, requirements and problems of diagnostics of complex industrial systems is discussed in this paper. Brief discussion given in Section 1 is particularly relevant to issues typical for chemical, petrochemical, power, food etc. large scale industrial installations. Section 2 of the paper lists and discusses main limitations and restrictions that should be taken into account in design phase of industrial diagnostic system. Basic issues are connected with variations in the diagnosed system structure, delays of fault symptoms causing false diagnoses, and necessity of isolation of multiple faults. Three applicable approaches of solving the issues stated in Section 2 are described in Section 3. Here, in Subsection 3.1, a novel and robust inference scheme against system structure variation is proposed (2) and Dynamic Decomposition of the Diagnosed System is briefly described. The problems of generation of false diagnoses caused by delays of fault symptoms are discussed in Subsection 3.2. As a remedy, a simple and robust algorithm on fault delays is presented. The discussion of applicable approach allowing handling multiple faults [9] is given in Subsection 3.3. The industrial pilot applications with use of advanced diagnostic and monitoring systems AMandD [16] and DiaSter [19] are presented in the summary part (Section 4). These systems make use, among others, from approaches presented in this paper.
7
Content available Multiple soft fault diagnosis of nonlinear dc circuits considering component tolerances
Tadeusiewicz M., Hałgas S.
Metrology and Measurement Systems
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2011
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Vol. 18, nr 3
349-360
EN
This paper is devoted to multiple soft fault diagnosis of analog nonlinear circuits. A two-stage algorithm is offered enabling us to locate the faulty circuit components and evaluate their values, considering the component tolerances. At first a preliminary diagnostic procedure is performed, under the assumption that the non-faulty components have nominal values, leading to approximate and tentative results. Then, they are corrected, taking into account the fact that the non-faulty components can assume arbitrary values within their tolerance ranges. This stage of the algorithm is carried out using the linear programming method. As a result some ranges are obtained including possible values of the faulty components. The proposed approach is illustrated with two numerical examples.
8
Content available Sensitivity analysis of multiple fault test and reliability measures in integrated GPS/INS systems
Almagbile A., Wang J., Ding W., Knight N.
Archiwum Fotogrametrii, Kartografii i Teledetekcji
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2011
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Vol. 22
25--37
EN
Based on Kalman filtering, multi-sensor navigation systems, such as the integrated GPS/INS system, are widely accepted to enhance the navigation solution for various applications. However, such integrated systems do not always provide robust and stable navigation solutions due to unmodelled measurements and system dynamic errors, such as faults that degrade the performance of Kalman filtering for such integration. Single fault detection methods based on least squares (snapshot) method were investigated extensively in the literature and found effective to detect the fault at either sensor level or integration level. However, the system might be contaminated by multiple faults simultaneously. Thus, there is an increased likelyhood that some of the faults may not be detected and identified correctly. This will degrade the accuracy of positioning. In this paper multiple fault test and reliability measures based on a snapshot method were implemented in both the measurement model and the predicted states model for use in a GPS/INS integration system. The influences of the correlation coefficients between fault test statistics on the performances of the faults test and reliability measures were also investigated. The results indicate that the multiple fault test and reliability measures can perform more effectively in the measurement model than the predicted states model due to weak geometric strength within the predicted states model.
9
Content available remote Multiple soft fault diagnosis of nonlinear circuits using the fault dictionary approach
Hałgas S.
Bulletin of the Polish Academy of Sciences. Technical Sciences
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2008
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Vol. 56, nr 1
53-57
EN
The paper deals with a multiple fault diagnosis of DC transistor circuits with limited accessible terminals for measurements. An algorithm for identifying faulty elements and evaluating their parameters is proposed. The method belongs to the category of simulation before test methods. The dictionary is generated on the basis of the families of characteristics expressing voltages at test nodes in terms of circuit parameters. To build the fault dictionary the n-dimensional surfaces are approximated by means of section-wise piecewise-linear functions (SPLF). The faulty parameters are identified using the patterns stored in the fault dictionary, the measured voltages at the test nodes and simple computations. The approach is described in detail for a double and triple fault diagnosis. Two numerical examples illustrate the proposed method.
10
Metoda wykrywania uszkodzeń parametrycznych w układach tranzystorowych
Tadeusiewicz M., Hałgas S., Sidyk P.
Elektronika : konstrukcje, technologie, zastosowania
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2007
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Vol. 48, nr 11
31-33
PL
Praca dotyczy badania uszkodzeń wielokrotnych o charakterze parametrycznym w układach tranzystorowych prądu stałego. Przedstawiono nową metodę potestową lokalizacji i identyfikacji uszkodzonych elementów przy ograniczonym dostępie do punktów testowych. W badaniach symulacyjnych uwzględniono silne nieliniowości wprowadzane przez tranzystory bipolarne. Metoda nie stawia bardzo rygorystycznych wymagań w zakresie dokładności pomiarowych. Może być uogólniona na obszerną klasę analogowych układów elektronicznych. Przytoczono przykład liczbowy ilustrujący zaproponowaną metodę i potwierdzający jej skuteczność.
EN
A method for multiple fault diagnosis in DC transistor circuits is developed in this paper. It deals with soft-faults, belongs to the class of simulation after test methods and gets along with strong nonlinearities introduced by the bipolar transistors. The method enables us to identify faulty elements and evaluate their values in the circuits with very limited accessible terminals for excitation and measurement. It does not require very high measurement precision. The method can be generalized to a broad class of electronic circuits. A numerical example illustrates the proposed approach and shows its efficiency.
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